Induction heating assembly for a vapour generating device

Abstract

An induction heating assembly for a vapour generating device comprises includes an induction coil and a heating compartment arranged to receive an induction heatable cartridge. A first electromagnetic shield layer is arranged outward of the induction coil and a second electromagnetic shield layer is arranged outward of the first electromagnetic shield layer. The first and second electromagnetic shield layers differ in one or both of their electrical conductivity and their magnetic permeability.

Claims

1. An induction heating assembly for a vapour generating device, the induction heating assembly comprising: an induction coil; a heating compartment arranged to receive an induction heatable cartridge; a first electromagnetic shield layer arranged outward of the induction coil; and a second electromagnetic shield layer arranged outward of the first electromagnetic shield layer; wherein the first and second electromagnetic shield layers differ in one or both of electrical conductivity and magnetic permeability.

2. The induction heating assembly according to claim 1, wherein: one of the electromagnetic shield layers comprises a ferrimagnetic, non-electrically conductive material; and the other of the electromagnetic shield layers comprises an electrically conductive material.

3. The induction heating assembly according to claim 1, wherein: the first electromagnetic shield layer comprises a ferrimagnetic, non-electrically conductive material; and the second electromagnetic shield layer comprises an electrically conductive material.

4. The induction heating assembly according to claim 1, wherein there is no electrically conductive material between the induction coil and the first electromagnetic shield layer.

5. The induction heating assembly according to claim 1, further comprising: a first insulating layer positioned between the induction coil and the first electromagnetic shield layer, wherein the first insulating layer is substantially non-electrically conductive and has a relative magnetic permeability substantially equal to 1.

6. The induction heating assembly according to claim 5, further comprising: an air passage from an air inlet to the heating compartment, wherein the air passage forms at least part of the first insulating layer.

7. The induction heating assembly according to claim 1, further comprising a housing, wherein the housing comprises the second electromagnetic shield layer.

8. The induction heating assembly according to claim 1, wherein one or both of the first and second electromagnetic shield layers are arranged circumferentially around the induction coil and at both first and second axial ends of the induction coil so as to substantially surround the induction coil.

9. The induction heating assembly according to claim 8, further comprising: an inhalation passage extending between the heating compartment and an air outlet at a first axial end of the induction heating assembly; wherein a portion of the inhalation passage extends in a direction substantially perpendicular to an axial direction between the heating compartment and the air outlet; and one or both of the first and second electromagnetic shield layers runs adjacent to said portion of the inhalation passage such that the first axial end of the induction coil is substantially covered by the one or both of the electromagnetic shield layers.

10. The induction heating assembly according to claim 1, further comprising a shielding coil positioned within the first or second electromagnetic shield layers at one or both of first and second axial ends of the induction coil.

11. The induction heating assembly according to claim 1, further comprising an outer housing layer surrounding the first and second electromagnetic shield layers.

12. An induction heating assembly for a vapour generating device, the induction heating assembly comprising: an induction coil; a heating compartment arranged to receive an induction heatable cartridge; an electromagnetic shield layer arranged outward of the induction coil, the electromagnetic shield layer comprising a ferrimagnetic, non-electrically conductive material; and a first insulating layer positioned between the induction coil and the electromagnetic shield layer, the first insulating layer comprising a material which is substantially non-electrically conductive and has a relative magnetic permeability substantially equal to 1.

13. The induction heating assembly according to claim 12, further comprising: a second insulating layer which is substantially non-electrically conductive and has a relative magnetic permeability less than, or substantially equal to, 1.

14. The induction heating assembly according to claim 13, wherein a part of the second insulating layer lies, in use, between the induction coil and a vaporisable substance inside the induction heatable cartridge.

15. A vapour generating device comprising: the induction heating assembly according to claim 12; an air inlet arranged to provide air to the heating compartment; and an air outlet in communication with the heating compartment.

16. The induction heating assembly according to claim 5, wherein the first insulating layer comprises air.

17. The induction heating assembly according to claim 13, wherein the second insulating layer comprises a plastics material.

18. A vapour generating device comprising: the induction heating assembly according to claim 1; an air inlet arranged to provide air to the heating compartment; and an air outlet in communication with the heating compartment.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a diagrammatic illustration of a vapour generating device comprising an induction heating assembly according to a first embodiment of the present disclosure;

(2) FIGS. 2 to 4 are diagrammatic illustrations of the shielding effect obtained by the use of an electromagnetic shield layer in accordance with aspects of the present disclosure and the variation in magnetic field strength that is obtained by the use of an insulating layer in accordance with aspects of the present disclosure;

(3) FIG. 5 is a diagrammatic illustration of part of an induction heating assembly according to a second embodiment of the present disclosure; and

(4) FIG. 6 is a diagrammatic illustration of part of an induction heating assembly according to a third embodiment of the present disclosure.

DETAILED DESCRIPTION OF EMBODIMENTS

(5) Embodiments of the present disclosure will now be described by way of example only and with reference to the accompanying drawings.

(6) Referring initially to FIG. 1, there is shown diagrammatically a vapour generating device 10 according to an example of the present disclosure. The vapour generating device 10 comprises a housing 12. When the device 10 is used for generating vapour to be inhaled, a mouthpiece 18 may be installed on the device 10 at an air outlet 19. The mouthpiece 18 provides the ability for a user to easily inhale vapour generated by the device 10. The device 10 includes a power source and control circuitry, designated by the reference numeral 20, which may be configured to operate at high frequency. The power source typically comprises one or more batteries which could, for example, be inductively rechargeable. The device 10 also includes an air inlet 21.

(7) The vapour generating device 10 comprises an induction heating assembly 22 for heating a vapour generating (i.e. vaporisable) substance. The induction heating assembly 22 comprises a generally cylindrical heating compartment 24 which is arranged to receive a correspondingly shaped generally cylindrical induction heatable cartridge 26 comprising a vaporisable substance 28 and one or more induction heatable susceptors 30. The induction heatable cartridge 26 typically comprises an outer layer or membrane to contain the vaporisable substance 28, with the outer layer or membrane being air permeable. For example, the induction heatable cartridge 26 may be a disposable cartridge 26 containing tobacco and at least one induction heatable susceptor 30.

(8) The induction heating assembly 22 comprises a helical induction coil 32 which extends around the cylindrical heating compartment 24 and which can be energised by the power source and control circuitry 20. As will be understood by those skilled in the art, when the induction coil 32 is energised, an alternating and time-varying electromagnetic field is produced. This couples with the one or more induction heatable susceptors 30 and generates eddy currents and/or hysteresis losses in the one or more induction heatable susceptors 30 causing them to heat up. The heat is then transferred from the one or more induction heatable susceptors 30 to the vaporisable substance 28, for example by conduction, radiation and convection.

(9) The induction heatable susceptor(s) 30 can be in direct or indirect contact with the vaporisable substance 28, such that when the susceptors 30 is/are inductively heated by the induction coil 32 of the induction heating assembly 22, heat is transferred from the susceptor(s) 30 to the vaporisable substance 28, to heat the vaporisable substance 28 and produce a vapour. The vaporisation of the vaporisable substance 28 is facilitated by the addition of air from the surrounding environment through the air inlet 21. The vapour generated by heating the vaporisable substance 28 then exits the heating compartment 24 through the air outlet 19 and may, for example, be inhaled by a user of the device 10 through the mouthpiece 18. The flow of air through the heating compartment 24, i.e. from the air inlet 21, through the heating compartment 24, along an inhalation passage 34 of the induction heating assembly 22, and out of the air outlet 19, can be aided by negative pressure created by a user drawing air from the air outlet 19 side of the device 10 using the mouthpiece 18.

(10) The induction heating assembly 22 comprises a first electromagnetic shield layer 36 arranged outward of the induction coil 32 and typically formed of a ferrimagnetic, non-electrically conductive material such as ferrite, Nickel Zinc Ferrite or mu-metal. In the embodiment shown in FIG. 1, the first electromagnetic shield layer 36 comprises a substantially cylindrical shield portion 38, for example in the form of a substantially cylindrical sleeve, which is positioned radially outwardly of the helical induction coil 32 so as to extend circumferentially around the induction coil 32. The substantially cylindrical shield portion 38 typically has a layer thickness (in the radial direction) of between approximately 1.7 mm and 2 mm. The first electromagnetic shield layer 36 also comprises a first annular shield portion 40, provided at a first axial end 14 of the induction heating assembly 22, which has a layer thickness (in the axial direction) of approximately 5 mm. The first electromagnetic shield layer 36 also comprises a second annular shield portion 42, provided at a second axial end 16 of the induction heating assembly 22. It will be noted that the second annular shield portion 42 comprises first and second layers 42a, 42b of shielding material between which an optional shielding coil 44 is positioned. In alternative embodiments, the second annular shield portion 42 may comprise a single layer of shielding material, either with or without the shielding coil 44 present.

(11) The induction heating assembly 22 comprises a second electromagnetic shield layer 46 arranged outward of the first electromagnetic shield layer 36. The second electromagnetic shield layer 46 typically comprises an electrically conductive material, for example a metal such as aluminium or copper, and may be in the form of a mesh. In the embodiment shown in FIG. 1, the second electromagnetic shield layer 46 comprises a substantially cylindrical shield portion 48, for example in the form of a substantially cylindrical sleeve having an axially extending circumferential gap (not shown), and an annular shield portion 50, provided at the first axial end 14 of the induction heating assembly 22. The substantially cylindrical shield portion 48 and the annular shield portion 50 may be integrally formed as a single component. In some embodiments, the second electromagnetic shield layer 46 has a layer thickness of approximately 0.15 mm. The resistance value of the second electromagnetic shield layer 46 is selected to minimise heating and conductive losses in the second electromagnetic shield layer 46, and may for example have a value of less than 30 mΩ.

(12) The induction heating assembly 22 comprises an outer housing layer 13 which surrounds the first and second electromagnetic shield layers 36, 46 and which constitutes the outermost layer of the housing 12. In an alternative embodiment (not illustrated), the outer housing layer 13 could be omitted such that the second electromagnetic shield layer 46 constitutes the outermost layer of the housing 12.

(13) The induction heating assembly 22 comprises a first insulating layer 52 which is positioned between the induction coil 32 and the first electromagnetic shield layer 36. The first insulating layer 52 is substantially non-electrically conductive and has a relative magnetic permeability substantially equal to 1, and in the illustrated embodiment the first insulating layer 52 comprises air.

(14) The provision of a first insulting layer 52 between the induction coil 32 and the first electromagnetic shield layer 36 advantageously ensures that an optimal electromagnetic field is generated for coupling with the susceptor(s) 30 of the induction heatable cartridge 26 and this is illustrated diagrammatically in FIGS. 2 to 4. For example, FIG. 2 illustrates diagrammatically the electromagnetic field that is generated by a helical induction coil 32 in the absence of the electromagnetic shield layers 36, 46 described above. FIG. 3, on the other hand, illustrates diagrammatically the electromagnetic field that is generated by the helical induction coil 32 when the first electromagnetic shield layer 36 described above, and in particular the substantially cylindrical shield portion 38, is positioned either very close to, or in contact with, the induction coil 32, in other words when the abovementioned first insulating layer 52 is not provided. It can be readily seen in FIG. 3 that although the first electromagnetic shield layer 36 reduces the strength of the electromagnetic field in a region radially outwardly of the first electromagnetic shield layer 36, and thereby reduces leakage of the electromagnetic field, it also reduces the strength of the electromagnetic field in a region radially inwardly of the induction coil 32 where the induction heatable cartridge 26 is positioned in use. This is undesirable because it adversely affects the coupling of the electromagnetic field with the susceptor(s) 30 of the induction heatable cartridge 26 and reduces heating efficiency. Referring finally to FIG. 4, it will be apparent that when a first insulating layer 52 in accordance with aspects of the present disclosure is positioned between the induction coil 32 and the first electromagnetic shield layer 36, the first electromagnetic shield layer 36, and in particular the substantially cylindrical shield portion 38, reduces the strength of the electromagnetic field in a region radially outwardly of the first electromagnetic shield layer 36, and thereby reduces leakage of the electromagnetic field, in a similar manner to that shown in FIG. 3. However, in contrast to FIG. 3, the strength of the electromagnetic field in the region radially inwardly of the induction coil 32, where the induction heatable cartridge 26 is positioned in use, is not reduced thereby ensuring optimum coupling of the electromagnetic field with the susceptor(s) 30 of the induction heatable cartridge 26 and maximising heating efficiency.

(15) Referring again to FIG. 1, it will be noted that the induction heating assembly 22 comprises an annular air passage 54 which extends from the air inlet 21 to the heating compartment 24. The air passage 54 is positioned radially outwardly of the induction coil 32, between the induction coil 32 and the first electromagnetic shield layer 36, and the first insulating layer 52 is formed at least in part by the air passage 54.

(16) The induction heating assembly 22 further comprises a second insulating layer 58. It will be seen in FIG. 1 that a first part 58a of the second insulating layer 58 is arranged on the inner side of the induction coil 32 so that it lies between the induction coil 32 and the vaporisable substance 28 inside the induction heatable cartridge 26. It will also be seen in FIG. 1 that a second part 58b of the second insulating layer 58 is arranged outwardly of the induction coil 32 and is positioned between the induction coil 32 and the first electromagnetic shield layer 36. In the illustrated embodiment, the second part 58b comprises a cylindrical sleeve 56 positioned radially outwardly of the annular air passage 54, adjacent to the first electromagnetic shield layer 36. The second insulating layer 58 is substantially non-electrically conductive and has a relative magnetic permeability less than, or substantially equal to, 1, and typically comprises a plastics material such as PEEK. As will be readily appreciated from FIG. 1, the first part 58a of the second insulating layer 58 defines the internal volume of the heating compartment 24 in which the induction heatable cartridge 26 is received in use.

(17) Referring now to FIG. 5, there is shown part of a second embodiment of an induction heating assembly 60 for a vapour generating device 10. The induction heating assembly 60 shown in FIG. 5 is similar to the induction heating assembly 22 shown in FIG. 1 and corresponding components are identified using the same reference numerals. It should be noted that the substantially cylindrical shield portions 38, 48 of the first and second electromagnetic shield layers 36, 46 have been omitted from FIG. 5.

(18) The induction heating assembly 60 comprises an inhalation passage 62 which extends from the heating compartment 24 to the air outlet 19 at the first axial end 14 of the induction heating assembly 60. The inhalation passage 62 comprises first and second axial portions 64, 66 which extend in a direction substantially parallel to the axial direction between the heating compartment 24 and the air outlet 19. The inhalation passage 62 also comprises a transverse portion 68 which extends in a direction substantially perpendicular to the axial direction between the heating compartment 24 and the air outlet 19. A plurality of electromagnetic shield assemblies, each comprising first and second electromagnetic shield layers 36, 46, are positioned to run adjacent to the transverse portion 68 of the inhalation passage 62 on opposite sides thereof. With this arrangement, the electromagnetic shield assemblies at least partially overlap each other so that the first axial end of the induction coil 32 is substantially shielded by the electromagnetic shield layers 36, 46.

(19) Referring now to FIG. 6, there is shown part of a third embodiment of an induction heating assembly 70 for a vapour generating device 10. The induction heating assembly 70 shown in FIG. 6 is similar to the induction heating assembly 60 shown in FIG. 5 and corresponding components are identified using the same reference numerals.

(20) The induction heating assembly 70 comprises an inhalation passage 72 which extends from the heating compartment 24 to the air outlet 19 at the first axial end 14 of the induction heating assembly 70. The inhalation passage 72 comprises first, second, third and fourth axial portions 74, 76, 78, 80 which extend in a direction substantially parallel to the axial direction between the heating compartment 24 and the air outlet 19. The inhalation passage 72 also comprises first, second and third transverse portions 82, 84, 86 which extend in a direction substantially perpendicular to the axial direction between the heating compartment 24 and the air outlet 19. A plurality of electromagnetic shield assemblies, each comprising first and second electromagnetic shield layers 36, 46, are again positioned to run adjacent to the transverse portions 82, 84, 86 of the inhalation passage 72 on opposite sides of the transverse portion 84. With this arrangement, it will again be seen that the electromagnetic shield assemblies at least partially overlap each other so that the first axial end of the induction coil 32 is substantially shielded by the electromagnetic shield layers 36, 46.

(21) Although exemplary embodiments have been described in the preceding paragraphs, it should be understood that various modifications may be made to those embodiments without departing from the scope of the appended claims. Thus, the breadth and scope of the claims should not be limited to the above-described exemplary embodiments.

(22) Unless the context clearly requires otherwise, throughout the description and the claims, the words “comprise”, “comprising”, and the like, are to be construed in an inclusive as opposed to an exclusive or exhaustive sense; that is to say, in the sense of “including, but not limited to”.